Hydraulic retractor control



Dec. 18, 1945. w. M. POHL HYDRAULIC RETRACTQR CONTROL Filed Oct. 1, 1941 2 Sheets-Sheet- 1 Dec. 18, 1945. w. M. POHL HYDRAULIC RETRACTOR CONTROL Filed 001:. 1, 1941 2 Sheets-Sheet 2 iqm N WNN . mm mm m RN tonneqs.

Patented Dec. 18, 1945 UNITED STATES PATENT OFFICE 7 HYDRAULIC RETRAC'I'OR CONTROL Walter M. Pohl, New Haven, Conn, assignor to Vickers, Incorporated, Dctroit,Mich., a corpo-V ration of Michigan Application October 1, 1941, Serial No. 413,126

SClaims.

This invention relates to a hydraulic retractor control and has particularly to do with an improved control system for a hydraulic motor.

This application is a continuation in part of my copending application Serial No. 318,255, filed February 10, 1940.

An object of the present invention is to provide a hydraulic control system in which a novel arrangement of valves permits the continued movement of a motor to be effected by slight movement of the motor by an external force in the particular direction concerned.

A further object of the invention is the provision of a system which may operate auto matically but may be fully controlled by manual operation. The hydraulic control system concerned herewith is especially adapted to the rammer mechanism of large guns in which it is desirable to have the retraction movement initiated by gun recoil. It is also adapted to a wide variety of commercial apparatus such as conveying machinery and the closing and opening of doors tion will now be described in connection with the drawings.

Referring to Fig. 1 a piston 80 having apiston rod 8| is located in a cylinder 82. A main pressure source I4 and a pilot pressure source I5 are provided, as are also a relief valve 60 and the pilot pressure accumulator 6|. A valve control housing is indicated generally at 83. In this valve control housing are formed valve bores 84, 85 and 88 and in an adjacent housing 81 Is formed a valve bore 88.

The right end, of cylinder 82, as viewed in the drawings, is connected to the valve block 83 by a conduit 88 which leads to valve bore 84. The left end of cylinder 82 is connected to the housing 83 by a conduit 90 which passes through the housing to connect to each of the valve bores 84, 85 and 88. A tank connection 9| connects to the valve bore 88 and a conduit 92 leading from pump I4 is connected t6 each of the valve bores '86, 85 and 84 consecutively. Valve bores 84 and 85 are each provided respectively with annular recesses 93 and 84 connected by a passage 95.

The conduit 82 terminates in an annular port 96 surrounding the bore 84. Slidable within the bore 84 is a plunger valve 98 urged downwardlyby a spring 99 which is received in an axial recess at the top of the plunger. The lower end of the plunger is tapered at I00 and provided with an axial recess IOI opening to the lower end of the valve and also to a transverse passage I02 which opens into the port 96. An annular restriction I03 is provided in the plunger 98 for purposes which will be described. In the lower portion of the bore 84 is a piston I05 which has a tapered end I06 upon which rests the tapered end I00 of plunger 98. In the top portion. of the bore 85 is a slidable plunger valve I08 urged downwardly by a spring I09 received in an axial recess in the plunger. The lower end of the plunger I08 is tapered as shown at III! and rests upon a tapered upper end III of a plunger II2 located in the lower portion of the bore 85. The tapered end H0 is provided with a restricted axial bore I I3 and cross bore I I4 connected to the hollow center, the purpose of which will be explained below.

-Slidably positioned in valve bore 86 is a valve spool II5 which is provided with enlarged heads H6, H1 and H8. A spring II9 acting on suitable washers serves to urge the valve II5 to the neutral position shown in the drawings. Directly below the valve I I5 is mounted a piston I2I shiftable in'housing 81.

Taking up now the pilot circuit, within the bore 88 in housing 81 is a pilot valve I23 centered by a spring I24 and provided with heads I25 and I26. Valve I23 receives pilot pressure from a conduit I21 and when in the position shown, it passes this pressure to a conduit I28 leading-up in the housing 83 between valve bores 84 and 85.

Valve bores 84 and 85 are each provided with an-:

nular ports I29 and I30, respectively,- which are connected to passage I28. Valve I23 is adapted to be shifted to direct pilot pressure either to the lower end or piston I05 or the lower end of piston II2 through conduits I3I and I32 leading to bores 84 and 85 respectively. Valve I23 is provided with an axial recess I33 which is open to the left end of the valve through a port I34 and which opens at the right end of the valve to a tank chamber I35. Conduit I35a connects chamber I35 to the tank. Spaced from ports I29 and I surrounding bores 84 and 85 aresimilar ports I36 and I31. The valve plunger 99 is provided with an annular restriction I38 which is adapted to connect the port I29 with the port I36 when the valve is shifted upwardly and which connects the port I36 with a tank port I39 when the valve plunger is in the position'shown. Valve plunger I08 is provided with an annular restriction I40 which is adapted to connect the port I30 with the port I31 when valve plunger I08 is shifted upwardly and which connects port I31 with a tank port I4I when the valve plunger I09 is in the position shown. Port I36 is connected by a conduit I43 t the top end 'of valve bore 86 and port I31 is connected to the lower end of piston I2I by a conduit I44. The chamber directly above the piston I2I is a tank chamber connected also to the chamber I35 at the right end of valve I23. The chamber behind valve I09 is connected through passage I09a and check valve I08b to conduit 90.

Fig. 1 shows the control system in neutral position with the pumps not running. When the pumps I4 and I5 are started, fluid from pump I4 will pass from conduit 92 up through the bore 96 around valve head II1 to the tank conduit 9I. Also the pilot pump I5 will deliver pressure to the accumulator piston 62 to lift the same and cause a spilling of pressure through the tank opening 63. In this manner a reserve supply of fluid is stored in the accumulator. A ramming stroke is initiated by manually shifting pilot valve I23 to the left by means of a hand lever I50. Shifting of this valve I23 will admit pilot pressure from the conduit I21 to conduit I3I and the lower working area of piston I05 to cause shifting of piston I05 and plunger valve 98 upward. In this position pilot pressure from conduit I28 may pass from port I29 to port I36 and then to the top of bore 96 to shift valve II5 down.

This shifting of valve II5 down will make a free connection between conduit 90 of cylinder 82 and tank conduit 9I and will also cause pressure from conduit 92 to pass the tapered ends I08 and I00 of piston I05 and valve plunger 99 to the conduit 89 and piston 80. As the piston 90 stands in the drawings, it has just completed a ramming stroke. During this advance stroke, valve plunger 98 was shifted to its upper position by piston I05. This initiated the stroke of piston 80 and during the stroke of piston 80 the valve plunger 98 was gradually returning to its static position (as shown in, Fig. 1) by reason of the fact that the spring 99 was urging the piston down and liquid was passing gradually from chamber 96 through restricted passages I02 and IOI to the chamber 94 behind the valve. The hand lever I 50 may be released without afiecting themotion of the motor. Inthe upp r position of valve 98, the conduit 89 is cut 011 from the ort 93. At the completion of the ramming stroke the piston 90 will be stopped by contact .with the cylinder 92 and by this time the valve 98 will probably have reached its position shown in Fig. 1. When valve 98 is fully restored to its lower position, the chamber at the upper part of the bore 86 will be vented thus allowing spring II9 to return valve II5 to its neutral position as shown. The flow from the operating pump I4 will then be diverted to th tank.

It is desirable that valve- 98 move to its upper or operative position quickly and move down to its static position slowly for which reason a check valve 99a to the left of valve 88 and restricted .motion of the valve.

valve is freely exhausted through the check valve 990, port 96, line 92, past valve II 5 to tank line 90-9I. As the valve 99 moves down, the incoming fluid is metered slowly through the restricted orifice IOI, thus retarding the downward The size of restriction IOI is important in that valve 99 must not reach a position closing 96 from 99 until th completion of the stroke of 80. If, however, an obstruction blocks the movement of the piston 90, valve 99 *Will continue to move to its down position to relieve pressure.

The rammer is especially useful for a short fast stroke and it is desirable that valve 98 reach a position closing 96 from 89 substantially at th end of the stroke of 90.

The retraction stroke may be initiated either by the manipulation of the control lever I50 or by a slight movement of the piston by the application of an extraneous force such as a gun recoil. When the hand lever I90 is used, the valve I23 will be shifted to the right and pilot pressure from conduit I21 will be admitted to conduit I32 and the lower end of bore 85. This will lift piston H2 and the plunger valve I09 50 that pilot pressure from conduit I29 may pass through port I30 to port I31 and conduit I44 to the lower end of piston I2 I This will shift valve II5 upwardly thereby blocking the tank conduit 9| and opening the conduit 90 to the pressure conduit 92. Pressur will then be directed to both ends of piston 90 since one end is in direct connection with conduit 90 and the right end will be connected to conduit 90 through valve bore 99, port 94, passage 95, port 93, valve bore 94, and conduit 89. As the effective area at the left end of the piston 90 is greater than the right end, the piston will advance to the right by the differential between the two hydraulic forces. Once the piston motion is started, valve- I09 will be maintained in open condition by virtue of the factthat flow from the lower end to the upper end of the valve I09 is through restricted orifices H3 and H4; the hand lever may be released without affecting the operating phase. This movement will continue until the piston is brought to rest by positive contact with the end of the cylinder at which time valve plunger I09 will be fully returned to its normal position by spring force, the lever I50 having been previously released. In this slow return movement valve I09 operates in the same manner as described in connection with valve 99.

The retraction motion may also be initiated by the extraneous force on the piston and the immediate effect of this force will be pressure on the lower end of plunger I09 through conduit 99, valve bore 04, port 93, passage and port 94. This pressure will shift valve I09 upwardly and connect conduit I29 and port I30 with port I91 and conduit I44. The result will be a shifting upwardly of the valve III as previously described in connection with the manual operation and the remainder of the action is the same.

The arrangement shown in Fig. 1 is designed to insure completion of the ramming stroke irrespective of the shifting of the control lever after the stroke has started; 1. e., after a ramming stroke has been initiated it will continue until completed, even though the control lever is shifted to the neutral or retract position. During the retraction stroke, however, the operator may take charge at any time and reverse the motion 1) shifting the control lever to Ram.

The operating principles which make this possible'will be clearly understood. During a ramming stroke valve is held in the ram position by pilot pressure applied to the large area 8. Shifting the control lever to retract admits the same pressure to the under side of small piston I2l, which tends to force it upward but is prevented from doing so because. of the greater force acting on valve H5 to hold it down. During a retraction stroke, however, valve 5 is held in the Retract position by pilot pressure applied to the small piston I2l, but .at any time during the retraction stroke the motion may be reversed by shifting the control lever to Ram," thereby admitting pilot pressure to the larger area-l It, at which time valve 5 will be shifted to .the ram position.

Some applications require that the retraction stroke be completed irrespective of the shifting said valves being retarded in movement from an source, a reversible motor means to be actuated by pressure from said source, said motor having a limited movement in each direction and a control system in a hydraulic circuit between said of the control lever but that it be possible for the operator to take charge and reverse the motion at any time during the ramming stroke. This may be accomplished-by modifying the design in accordance with Fig, 2, in which piston l2 la is made with a greater area than that of I I6. Fig. 3 shows a further modification in which it is possible for the operator to take charge and reverse the motion at any time during either the ramming or retraction stroke. In this design areas I2") and H6 are equal and if pilot pressure is applied to both at the same time the hydraulic forces acting on valve H5 will be balanced and it will be returned to neutral bythe centering spring, thus diverting flow from pump M to tank. The immediate efiect of this willbe a momentary stopping of piston 80 while valve 98 or Hi8 (as the case may be) recovers its normal spring impelled position, after which motion of the piston will take place in the direction required by 'the position of the control lever.

A check valve I55 in conduit 9| connects the tank with valve recess 86. This check valve functions only during the period that piston 80 is being moved in the retract direction'by an extraneous force. Its purpose is to permit oil to be drawn into the cylinder directly from the tank, thus assuring an ample supply of oil to replace the vacuum,which' would otherwise be created by the retreating piston. At such times,

if the piston velocity is quite high, the pump would not have sufficient necessary fluid;

What I claim is:

1. In a hydraulic system, a main pressure source, a reversible motor means 'to be actuated by pressure from said source, said motor having a limited movement in each direction and a control system in a hydraulic circuit between said' pressure source and said motor comprising a capacity to supply the source of pilot pressure, a main valve for controlling the direction of movement of said motor by controlling the output of said main pressure source, a pilot pressure chamber at each end of said valve to permit the same to be pilot operated, a manually operable pilot control valve for directing pressure from said pilot source, a first auxiliary valve shiftable from a static position in response to pilot pressure from said manually operated pilot valve to an operating position for directing pilot pressure to one end of said main valve, and a second auxiliary control valve shift-- able from a static position in response to pilot pressure from said manually operated control valve to an operating position adapted to direct pilot pressure to the other of said main valve pilot chambers, means tending to move each of said auxiliary valves to static position, each of auxiliary valve shiftable from a static position in response to pilot pressure from said manually operated pilot valve to an operating position for directing pilot pressure to one end of said main valve, and asecond auxiliary controlvalve shiftable from a static position in response to pilot pressure from said manually operated control valve to an operating position adapted to direct pilot pressure to the other of said main valve pilot chambers, means tending to move each of said auxiliary valves to static position, each of said valves being retarded in movementirom an operative position to a static position after initial shifting to operative position by reason of a restricted passage connecting a closed chamber at one end of the valve to operating pressure at the other end of the valve, one of said auxiliary valves being responsive to movement of said motor by an external force in a direction opposite to that instituted by the other auxiliary valve to efiect continued operation of said motor in the direction instituted by the external force.

3. In a hydraulic system, a pressure source, a motor means to be'actuated by pressure from said source, control valve means for directing liquid under pressure from said source to said motor to control the starting, stopping and direction thereof, pilot chambers at each end of ,said control valve to effect shifting thereof, and pilot valve means for directing pressure to said chambers selectively and simultaneously to control the position of said control valve, the efiectivev pressure areas in said pilot chambers being related to efiect predetermined shifting and consequent changein the position and function of said control valve during periods when pressure is .di-

rected simultaneously to said pilot chambers by source of pilot pressure, a series of three valves connected to control said pilot pressure, two of said three valves being arranged to control, alternately, shifting of said mainpilot valve means, and one of s'aidthree valves being arranged to control shifting of said other two valves.

5. In a power transmission system, a hydraulic motor, a source of pressure for driving said motor, a main pilot valve means for controlling the flow or pressure liquid to and from said motor, a source of pilot pressure, a series of three valves connected to control said pilot pressure, two of said three valves being shiftable from neutral to operative positions to control, alternately, shifting of said main pilot valve means, and the third of said three valves being arranged to control shifting of said first two valves, said first two valves each comprising a valve member slidable in a bore and provided with restricted passages between the ends thereof arranged to be subject to motor operating pressure when either of the first two valves is actuated from neutral, meansbiasing each of said valves toward a neutral position, closed chambers behind said first two valves whereby pressure passes through said passages to said chamber subsequent to actuation of one of said first two valves to efiect delayed restoration of the shifted valve to neutral.

6. In a power transmission system, a hydraulic motor, a source of pressure for driving said motor, a main pilot valve means for controlling the flow of pressure liquid to and from said motor, a source of pilot pressure, a series of three valves connected to control said pilot pressure, two of said three valves being shiftable from neutral to operative positions to control, alternately, shifting of said main pilot valve means, and the third of said three valves being arranged to control shifting of said other first two valves, said first two valves each comprising a valve member slidable in a bore and provided with restricted passages between the ends thereof arranged to be subject to motor operating pressure when a valve is actuated from neutral, closed chambers behind said valves, whereby pressure passes through said passages to said chamber subsequent to actuation of either of said first two valves to effect delayed restoration of the shifted valve to neutral, and means connecting each of said, chambers to a motor operating pressure line arranged to permit exhaust of said chamber during movement of its respective valve and to prevent exhaust during operation of said motor.

7. In a power transmission system, a hydraulic motor, a source of pressure for driving said motor, a main pilot valve means for controlling the flow of pressure liquid to and from said motor, a source of pilot pressure, and two valves connected to control said pilot pressure and arranged to control alternately, shifting of said main pilot valve means, said two valves each comprising a valve member slidable in a bore from a neutral to operative position and provided with restricted passages between the ends thereof arranged to be subject to motor operating pressure when either of said two valves is actuated from neutral. closed chambers behind said two valves whereby pressure passes through said passages to said chambers subsequent to actuation of one of said two valves to effect delayed restoration of the shifted valve to neutral.

8. In a power transmission system, a hydraulic motor, a source of pressure for driving said motor, a main pilot valve means for controlling the flow of pressure liquid to and from said motor, a source of pilot pressure, and two valves connected to control said pilot pressure and arranged to control, alternately, shifting of said pilot means, said two valves each comprising a valve member slidable in a bore from a neutral to operative position and provided with restricted passages between the ends thereof arranged to be subject to motor operating pressure when either of the two valves is actuated from neutral, closed chambers behind said valves whereby pressure passes through said passages to said chambers subsequent to actuation of one of said valves to effect delayed restoration of the shifted valve to neutral, and means connecting each of said chambers to a motor operating pressure line arranged to permit exhaust of said chamber during movement of its respective valve and to prevent exhaust during operation of said motor.

WALTER M. POHL. 

